Radial nerve dysfunction is a problem with the movement or sensation of the back of the arm (triceps), the forearm, or the hand.

Radial nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the radial nerve, which travels down the arm and supplies movement to the triceps muscle at the back of the upper arm. It also provides extension to the wrist and helps in movement and sensation of the wrist and hand.

Dysfunction of a single nerve group (such as the radial nerve) is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage (such as that which occurs with mononeuritis multiplex).

The usual causes are direct trauma, prolonged pressure on the nerve, or compression of the nerve caused by swelling or injury of nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.

The radial nerve may be injured at the axilla (underarm) by direct pressure, such as "crutch palsy," caused by improper use of crutches, or pressure caused by hanging the arm over the back of a chair.

A more common cause of radial nerve dysfunction is trauma that occurs in the upper arm, such as a fracture of the humerus (upper arm bone) or pressure to the upper arm from arm positions during sleep or coma.

"Saturday-night palsy" is a term for an injury that occurs to the radial nerve during deep sleep, such as that which may occur when a person is intoxicated. Prolonged or repeated constriction of the wrist (caused by wearing a tight watch strap, for example) may also cause an injury to terminal portions of the radial nerve.

In some cases, no detectable cause can be identified. These mechanical factors may be complicated by ischemia (lack of oxygen from decreased blood flow) in the area.

Symptoms can affect the following:

• The hand or forearm (dorsal surface, the "back" of the hand)
• The "thumb side" (radial surface) of the dorsal hand
• The fingers nearest the thumb (2nd and 3rd)

The following symptoms may occur:

• Numbness, decreased sensation, tingling, or burning sensation
• Pain
• Abnormal sensations
• Difficulty extending the arm at the elbow
• Difficulty extending the wrist

A neuromuscular examination of the arm, hand, and wrist may identify radial nerve dysfunction. There may be weakness of the wrist and finger extension muscles with decreased ability to extend the arm at the elbow, a minor decreased ability to rotate the arm outward (supination), or difficulty lifting the wrist or fingers (extensor muscle weakness).

Wrist drop or finger drop may be present, or there may be atrophy (muscle loss) of some of the muscles of the forearm. A detailed patient history may be needed to determine the possible cause of the neuropathy. Rarely, radial nerve dysfunction may be difficult to differentiate from a stroke in the brain.

Tests that reveal nerve dysfunction may include:

• EMG (a recording of electrical activity in muscles)
• Nerve conduction tests
• Nerve biopsy

Head, neck, and shoulder MRIs can help rule out other conditions with similar symptoms.